1. Field of the Invention
The present invention relates to a light device and more particularly to a high thermal diffusion efficiency light device.
2. Description of Related Art
Apparatus, such as projectors, that use light devices to project light are moving towards light, thin, and small design so as to meet requirement of convenience. However, the surface temperature of the light device will increase when the size of the light device shrinks. An incandescent light bulb in the light device will produce heat to rapidly increase temperature of the case of such a small light device. Therefore, the surface temperatures of the light device and the projector will exceed the limitation of safety and may burn to hurt a user. Such products are never allowed to sell because of safety.
The surface temperature is not an issue for a large light device due to enough thermal diffusion space. However, the surface temperature becomes a critical issue when it comes to a small light device. The restricted thermal diffusion space of the small light device will result in increased surface temperature. For example, the gap of a common projector between the light bulb and the case is about 1 to 2 centimeters high. Thermal problems of such size projector can be easily solved by a common air flow inlet and a fan that generates air flow. Factors that influence thermal diffusion efficiency, such as air flow path and diffusion plate, are not necessarily optimized. However, for a small light device, the size of the light bulb may be shrunken to only several square centimeters. Diffusing heat area is decreased and thermal radiation effects are increased quickly because the light bulb and the case are getting closer. There are only some easy heat diffusion methods in prior art for most traditional large projectors. For example, a case is provided to cover the light bulb and a fan is used to supply air flow; however, the air flow is not guided to perform high efficient diffusion. Most of the air flow flows randomly and does not contribute much in thermal diffusion. The light bulb is simply covered by the case and not much effort is made to restrict and make use of the air flow.
Furthermore, prior art projectors do not provide efficient shield against thermal radiation. Heat insulation material and heat reflectors are usually provided to insulate heat. However, the heat insulation material is costly. The increase in heat insulation cost is proportional to the square of increase in heat insulation efficiency. Therefore it is not practical in mass production of projectors. Further, the insulation material will add thickness to the projector. For enough insulation, the insulation material must have a certain thickness. However, the thickness will increase the size of the light device and consequently prohibits the light device from meeting the requirement of small size. The thickness is usually required to be as thin as 1 mm for a small light device in providing enough heat insulation. Such a little size is impossible for normal insulation material.
It is necessary to provide a solution to the above problems for a small light device, particularly in diffusion air flow and radiation insulation. The present invention aims to solve the problems and provides an effective solution.
The present invention discloses a light device including a light bulb set and a thermal diffusion guide disposed around the light bulb set. The light bulb set is a projection light bulb having an outer wall. The projecting light bulb is made of a luminous body and a light reflecting mask, which can be done by persons in the art and therefore will not be further described herein. The thermal diffusion guide keeps a distance from the outer wall in order to form an air passage for restricting air flow to flow through. The thermal diffusion guide has an outer rim forming a first air gap between the outer rim and the outer wall for allowing the air flow to flow into the air passage.
By the air passage, all the air flow can be effectively restricted and utilized to carry away heat for increasing thermal diffusion efficiency. And, through the first air surface, all the air flow can be restricted to pass around the light bulb set in avoidance of air flow waste and low diffusion efficiency caused by unrestricted air flow.
Preferably, the thermal diffusion guide further includes a cavity near the outer rim. The cavity forms a second air gap above the outer wall for allowing more air to flow into the air passage.
The second air surface can increase inlet air flow and to enhance the capacity of carrying away the heat.
Preferably the thermal diffusion guide further includes a narrow portion that keeps a short distance from the outer wall to form a rapid air passage. Heat is thereby rapidly removed in a limited space and thermal diffusion efficiency is increased.
To avoid overheating, the present invention further discloses a light device including a light bulb set, a shield above the light bulb set, and a diffusion plate above the shield. Wherein, a first isolation layer is formed between the shield and the diffusion plate. The light device may further include a case disposed above the diffusion plate and a second isolation layer is formed between the diffusion plate and the case.
Most of the thermal radiation is blocked by the shield from flowing outwards to device surface. The diffusion plate then disperses heat by thermal conductivity. The heat is carried away to avoid heat accumulation around the light bulb set. And the first isolation layer further reduces outward heat diffusion. The first isolation layer can be an air layer or a vacuum layer. By the introduction of the above, heat can be restricted from flowing outwards and the rest of the heat that is not blocked by the shield is further dispersed. Therefore, surface temperature is greatly lowered within limited space.
The shield may partially contact with the light bulb set and under such a circumstance the shield includes an interruption area disposed around the contact portion of the shield and the light bulb set.
Preferably the shield is high in radiation reflectivity and low in thermal conductivity. For example, the shield is made of alloy or stainless steel. The diffusion plate is preferably high in thermal conductivity. For example, the diffusion plate is a metal plate, a copper metal plate or an aluminum metal plate.
By the disclosure of the present invention, heat can be rapidly removed within limited space and a light device that meets safety requirement is provided.